The URL can be used to link to this page

Home My WebLink AboutMAVERIK CONVENIENCE STORE & FUEL SALES - PDP - PDP150028 - REPORTS - DRAINAGE REPORT` Preliminary Drainage Report for Maverik City of Fort Collins, Colorado Developer: Maverik Inc 880 West Center Street Salt Lake City, UT 84054 801.335.3851 Contact: Don Lilyquist Engineer: Atwell, LLC 143 Union Blvd, Suite 700 Lakewood, CO 80228 303.462.1100 Project Number 15001770 January, 2016 I hereby certify that this Preliminary Drainage Report for the design of Maverik was prepared by me or under my direct supervision in accordance with the provisions of the Urban Drainage and Flood Control District Manual and the Fort Collins Amendments for the owners thereof. I understand that the City of Fort Collins does not and will not assume liability for drainage facilities designed by others. ______________________________ Registered Professional Engineer State of Colorado No. ________ I hereby certify that the drainage facilities for Maverik shall be constructed according to the design presented in this report. I understand that the City of Fort Collins does not and will not assume liability for the drainage facilities designed and/or certified by my engineer. I understand that the City of Fort Collins review drainage plans but cannot, on behalf of Maverik, guarantee that final drainage design review will absolve The Maverik, LLC and/or their successors and/or assigns of future liability for improper design. I further understand that approval of the Final Development Plan does not imply approval of my engineer’s drainage design. _________________________________ Name of Developer _________________________________ Authorized Signature Date Table of Contents General Location and Description 1 Drainage Basins and Sub-Basins 1 Drainage Design Criteria 3 Drainage Facility Design 3 Conclusions 3 References 4 Appendix A – Maps & Figures Hydrologic Soils Report Rainfall Intensity Runoff Coefficients Appendix B – Stormwater Calculations Composite Run-off Coefficients Time of Concentration Minor Storm Runoff Calculations Major Storm Runoff Calculations Detention Volume by Modified FAA Method Existing Pond Volume Historic Drainage Plan Back Pocket Preliminary Drainage Plan Back Pocket ATWELL, LLC Preliminary Drainage Report Maverik PAGE 1 I. General Location and Description The purpose of this report is to provide a guide for the City of Fort Collins and the developer to use for the planning and final design of drainage facilities for the Maverik development site. The Maverik development site occupies 1.77 acres that includes Lot 2 of Maverik Subdivision Filing No. 1 and Lot 17 of Interchange Business Park. The site is located within the Northwest one-quarter of Section 15, Township 7 North, Range 68 West of the 6th Principal Meridian. The parcel’s street frontage is along I-25 Frontage Road with an address of 4333 E. Mulberry Street. The site is bounded by Lot 1 of Maverik Subdivision Filing No. 1 to the south and west (containing the Americas Best Value Inn & Suites property); Frontage Road to the east; and CDOT ROW for Intersate-25 to the north. A vicinity map is included within Appendix A of this report. The proposed development site currently has a round brick building that formerly served as a restaurant. The east side of the site generally slopes from north to south at about a 1 percent grade, while the west side generally slopes from east to west. Both sides of the site drain to grated inlets within the existing parking lot that discharge flow into an existing detention pond on the north side of the site. This detention pond has a 24” controlled outlet pipe that discharges to a roadside drainage swale along the I-25 off-ramp to E. Mulberry Street. Soils on the site are identified as Fort Collins loam, which is a Hydrologic Group B soil. Refer to the soils map in Appendix A of this report for additional soils information. The proposed use for the redeveloped property is a convenience store & fueling station. The proposed development will contain a convenience store replacing the existing restaurant building along with the fueling station to the northeast with surrounding parking. A rest area with tot lot and dog park will also be provided. The development parcel lies within the limits of the Boxelder Creek Regional Master Plan. The development site is identified as outside of the 100-yr floodplain (Zone X) as shown on the flood insurance rate map number 08069C1003G, dated May 2, 2012. II. Drainage Basins and Sub-Basins As stated in section I, the east side of the site generally slopes from north to south at about 1 percent, while the west side generally slopes from east to west. Both the existing ATWELL, LLC Preliminary Drainage Report Maverik PAGE 2 Americas Best Value Inn & Suites property and the proposed Maverik site will be analyzed as they both drain to an existing detention pond in the northwest corner of the property. The outfall drainage way is identified as a tributary of Boxelder Creek in the aforementioned Regional Master Plan. Under existing conditions, runoff from the site reaches the outfall drainage way via area drains in the parking lot on the south side of the site and west of the pond. Overall the site (including the Americas Best Value Inn and Suites) has been divided into three main basins (A, B, and C) with Basin A being split into two-sub basins: Sub-Basin A1: (2.85 acres; Q100 = 15.4 cfs) Sub-Basin A1 contains most of the existing Americas Best Value Inn & Suites site including the building, pool area and surrounding parking. The existing detention pond and southwest half of the proposed convenience store are also contained in Sub-Basin A1. All flows in Sub-Basin A1 will drain to the existing detention pond through the existing storm sewer system located on site. Sub-Basin A2: (1.54 acres; Q100 = 9.0 cfs) Sub-Basin A2 contains most of the new construction including the northeast half of the convenience store, the new canopy, most of the parking lot, and the recreation area & dog park. Sub-Basin A2 drains to an existing grated inlet near the south driveway entrance which then conveys the flows to the existing detention pond. Basin B: (0.05 acres; Q100 = 0.2 cfs) Basin B consists of a small strip of land in the northern corner of the site. The basin drains to the existing roadside ditch that is along the access road to the north and west of the site. Drainage from Basin B does not flow to the existing detention pond. Basin C: (0.12 acres; Q100 = 0.5 cfs) Basin C consists of a small strip of land on the southwest and southeast sides of the site between the existing parking area and property line. This small area sheet flows offsite to Frontage Road and the adjacent property to the southwest. Historic basins follow the same layout as the proposed basins with the only changes being small variance in size due to the convenience store building replacing the restaurant building. Historic basins are as follows: Historic Sub-Basin A1: 2.92 acres; Q100 = 16.0 cfs Historic Sub-Basin A2: 1.43 acres; Q100 = 7.6 cfs ATWELL, LLC Preliminary Drainage Report Maverik PAGE 3 Historic Basin B: 0.09 acres; Q100 = 0.3 cfs Historic Basin C: 0.12 acres; Q100 = 0.5 cfs III. Drainage Design Criteria Drainage analysis and facility design has been prepared in accordance with UDFCD Standards and the Fort Collins Amendments to the Standards. The City of Fort Collins Low Impact Development (LID) requirements state that 25% of vehicle use pavements be pervious and 50% of impervious area be treated by LID techniques. Even though the site is existing and impervious amounts are only increasing from 78% to 81.5%, the site will feature several LID techniques. Approximately 4000 sf of updated parking area will utilize permeable pavers. Planters and trees will be added throughout the site including along perimeter roads and parking islands. Vegetative buffers will also be utilized along walks and parking areas. IV. Drainage Facility Design The existing on-site detention pond will be reused in its’ existing location. The existing detention pond was found to have a capacity of 0.35 acre-feet with a depth of just less than four feet. No existing outlet structure or spillway was found on the existing pond. Pond release is controlled by the existing 24” RCP pipe at the low end of the pond. The pond drains to the existing swale along the access road just beyond the northwest property line. In-flow to the pond comes from two existing 18” RCP pipes that connect to the existing storm sewer system on site. The storm sewer system and inlet pipes will remain. Proposed updates to the detention pond include raising the berm around the perimeter of the pond approximately 1.5 feet to increase pond volume to 0.46 acre-feet and provide a minimum of 1 foot of freeboard around the pond. An emergency spillway draining to the adjacent roadside ditch will also be provided. V. Conclusions This study is in compliance with the Urban Storm Drainage Criteria Manual and the Fort Collins Amendments. This study is also consistent with the overall drainage concept in previously prepared regional drainage study (References 3). The proposed development and proposed drainage facilities will result in no adverse impacts created by the quantity or quality of storm water generated by this project. ATWELL, LLC Preliminary Drainage Report Maverik PAGE 4 VII. References 1. Urban Storm Drainage Criteria Manual; Denver Regional Council of Governments; August 2011. 2. Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual; City of Fort Collins; December 12, 2012 3. Final Boxelder Creek Regional Stormwater Master Plan; Larimer County & Boxelder Creek Regional Alliance; October 2006 4. Floor Insurance Rate Map, Larimer County, Map Number 08069C1003G; Federal Emergency Management Agency; May 2, 2012 Appendix A Maps & Figures Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/16/2015 Page 1 of 4 4491990 4492030 4492070 4492110 4492150 4492190 4492230 4492270 4491990 4492030 4492070 4492110 4492150 4492190 4492230 4492270 499960 500000 500040 500080 500120 500160 500200 500240 500280 500320 500360 499960 500000 500040 500080 500120 500160 500200 500240 500280 500320 500360 40° 34' 52'' N 105° 0' 2'' W 40° 34' 52'' N 104° 59' 43'' W 40° 34' 43'' N 105° 0' 2'' W 40° 34' 43'' N 104° 59' 43'' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 50 100 200 300 Feet 0 30 60 120 180 Meters Map Scale: 1:2,030 if printed on A landscape (11" x 8.5") sheet. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Hydrologic Soil Group Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 34 Fort Collins loam, 0 to 1 percent slopes B 10.9 63.6% 73 Nunn clay loam, 0 to 1 percent slopes C 5.5 32.3% 76 Nunn clay loam, wet, 1 to 3 percent slopes C 0.7 4.1% Totals for Area of Interest 17.1 100.0% Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/16/2015 Page 3 of 4 Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/16/2015 Page 4 of 4 33 (11) Section 4.0 is amended to read as follows: 4.0 Intensity-Duration-Frequency Curves for Rational Method: The one-hour rainfall Intensity-Duration-Frequency tables for use the Rational Method of runoff analysis are provided in Table RA-7 and in Table RA-8. Table RA-7 -- City of Fort Collins Rainfall Intensity-Duration-Frequency Table for Use with the Rational Method (5 minutes to 30 minutes) 2-Year 10-Year 100-Year Duration (min) Intensity (in/hr) Intensity (in/hr) Intensity (in/hr) 5 2.85 4.87 9.95 6 2.67 4.56 9.31 7 2.52 4.31 8.8 8 2.4 4.1 8.38 9 2.3 3.93 8.03 10 2.21 3.78 7.72 11 2.13 3.63 7.42 12 2.05 3.5 7.16 13 1.98 3.39 6.92 14 1.92 3.29 6.71 15 1.87 3.19 6.52 16 1.81 3.08 6.3 17 1.75 2.99 6.1 18 1.7 2.9 5.92 19 1.65 2.82 5.75 20 1.61 2.74 5.6 21 1.56 2.67 5.46 22 1.53 2.61 5.32 23 1.49 2.55 5.2 24 1.46 2.49 5.09 25 1.43 2.44 4.98 26 1.4 2.39 4.87 27 1.37 2.34 4.78 28 1.34 2.29 4.69 29 1.32 2.25 4.6 30 1.3 2.21 4.52 34 Table RA-8 -- City of Fort Collins Rainfall Intensity-Duration-Frequency Table for Use with the Rational Method (31 minutes to 60 minutes) 2-Year 10-Year 100-Year Duration (min) Intensity (in/hr) Intensity (in/hr) Intensity (in/hr) 31 1.27 2.16 4.42 32 1.24 2.12 4.33 33 1.22 2.08 4.24 34 1.19 2.04 4.16 35 1.17 2.0 4.08 36 1.15 1.96 4.01 37 1.16 1.93 3.93 38 1.11 1.89 3.87 39 1.09 1.86 3.8 40 1.07 1.83 3.74 41 1.05 1.8 3.68 42 1.04 1.77 3.62 43 1.02 1.74 3.56 44 1.01 1.72 3.51 45 0.99 1.69 3.46 46 0.98 1.67 3.41 47 0.96 1.64 3.36 48 0.95 1.62 3.31 49 0.94 1.6 3.27 50 0.92 1.58 3.23 51 0.91 1.56 3.18 52 0.9 1.54 3.14 53 0.89 1.52 3.1 54 0.88 1.5 3.07 55 0.87 1.48 3.03 56 0.86 1.47 2.99 57 0.85 1.45 2.96 58 0.84 1.43 2.92 59 0.83 1.42 2.89 60 0.82 1.4 2.86 36 RAINFALL INTENSITY-DURATION-FREQUENCY CURVE 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 0.00 10.00 20.00 30.00 40.00 50.00 60.00 STORM DURATION (minutes) RAINFALL INTENSITY (inches/hour) 2-Year Storm 10-Year Storm 100-Year Storm Figure RA-16 City of Fort Collins Rainfall Intensity-Duration-Frequency Curves (13) Section 5.0 is deleted in its entirety. (14) Section 6.0 is deleted in its entirety. (15) Section 7.0 is deleted in its entirety. (16) Section 7.1 is deleted in its entirety. (17) Section 7.2 is deleted in its entirety. (18) Section 7.3 is deleted in its entirety. (19) Section 8.0 is deleted in its entirety. (20) Table RA-1 is deleted in its entirety. 41 Table RO-11 Rational Method Runoff Coefficients for Composite Analysis Character of Surface Runoff Coefficient Streets, Parking Lots, Drives: Asphalt 0.95 Concrete 0.95 Gravel 0.5 Roofs 0.95 Recycled Asphalt 0.8 Lawns, Sandy Soil: Flat <2% 0.1 Average 2 to 7% 0.15 Steep >7% 0.2 Lawns, Heavy Soil: Flat <2% 0.2 Average 2 to 7% 0.25 Steep >7% 0.35 (4) A new Section 2.9 is added, to read as follows: 2.9 Composite Runoff Coefficient Drainage sub-basins are frequently composed of land that has multiple surfaces or zoning classifications. In such cases a composite runoff coefficient must be calculated for any given drainage sub-basin. The composite runoff coefficient is obtained using the following formula:   t n i i i A C A C    1 * (RO-8) Where: C = Composite Runoff Coefficient Ci = Runoff Coefficient for Specific Area (Ai) Ai = Area of Surface with Runoff Coefficient of Ci, acres or feet2 n = Number of different surfaces to be considered At = Total Area over which C is applicable, acres or feet2 (5) A new Section 2.10 is added, to read as follows: Appendix B Stormwater Calculations COMPOSITE C-FACTOR & WEIGHTED PERCENT IMPERVIOUSNESS ANALYSIS Maverik ATWELL GDB Date: January 2016 Runoff Coefficients C2 C5 C10 C100 I (%) Asphalt/Concrete/Roofs 0.79 0.81 0.83 0.88 95.0% (Table RO-5 & RO-11) Pavers 0.29 0.35 0.40 0.52 50.0% (Table RO-5 & RO-11) Lawns 0.06 0.14 0.22 0.40 10.0% (Table RO-5 & RO-11) Total Area A/C/R Pavers Lawns Area Check BASIN (AC) (AC) (AC) (AC) (AC) Comp. C2 Comp. C5 Comp. C10 Comp. C100 Comp. I (%) Hist A1 2.92 2.54 0.00 0.38 Ok 0.70 0.72 0.75 0.82 83.9% Hist A2 1.43 0.94 0.00 0.49 Ok 0.54 0.58 0.62 0.72 65.9% 4.35 3.48 0.00 0.87 Ok 0.64 0.68 0.71 0.78 78.0% Hist B 0.09 0.00 0.00 0.09 Ok 0.06 0.14 0.22 0.40 10.0% Hist C 0.12 0.00 0.00 0.12 Ok 0.06 0.14 0.22 0.40 10.0% A1 2.85 2.42 0.00 0.43 Ok 0.68 0.71 0.74 0.81 82.2% A2 1.54 1.23 0.09 0.22 Ok 0.66 0.69 0.72 0.79 80.2% 4.39 3.65 0.09 0.65 Ok 0.67 0.70 0.73 0.80 81.5% B 0.05 0.00 0.00 0.05 Ok 0.06 0.14 0.22 0.40 10.0% C 0.12 0.00 0.00 0.12 Ok 0.06 0.14 0.22 0.40 10.0% STANDARD FORM SF-2 TIME OF CONCENTRATION SUBDIVISION: Maverik CALCULATED BY: GDB DATE: Jan-16 SUB-BASIN DATA INITIAL/OVERLAND TRAVEL TIME Tc CHECK FINAL REMARKS TIME (Tc) (Tt) (Urbanized Basins) Tc DESIG: AREA C5 LENGTH AVG. SLOPE Ti LENGTH AVG. SLOPE VEL Tt COMP TOTAL Tc=(L/180)+10 (acres) (ft) (%) (min) (ft) (%) (fps) (min) Tc LENGTH (ft) (min) (min) Hist A1 2.92 0.71 200 2.0 7.9 530 1.0 0.7 12.6 20.5 730 14.1 14.1 Hist A2 1.43 0.69 65 2.0 4.7 270 1.0 0.7 6.4 11.2 335 11.9 11.2 Hist B 0.09 0.14 30 4.0 6.0 0 2.0 1.0 6.0 30 10.2 6.0 Hist C 0.12 0.14 5 10.0 1.8 0 2.0 1.0 1.8 5 10.0 5.0 A1 2.85 0.71 200 2.0 7.9 530 1.0 0.7 12.6 20.5 730 14.1 14.1 A2 1.54 0.69 65 2.0 4.7 270 1.0 0.7 6.4 11.2 335 11.9 11.2 B 0.05 0.14 254.0 5.5 0 2.0 1.0 5.5 25 10.1 5.5 C 0.12 0.14510.0 1.8 0 2.0 1.0 1.8 5 10.0 5.0 GDB JOB NO: DATE: Jan-16 PROJECT: Maverik CHECKED BY: DESIGN STORM: 2-year DESCRIPTION DESIGN POINT AREA DESIG. AREA (Acres) RUNOFF COEFF Tc (min) C A (Acres) I (in/hour) Q (cfs) Tc (min) (C A) (Acres) I (in/hour) Q (cfs) SLOPE (%) STREET FLOW (cfs) DESIGN FLOW (cfs) SLOPE (%) PIPE SIZE (in.) LENGTH (ft) VELOCITY (fps) Tt (min) REMARKS 1 Hist A1 2.92 0.70 14.1 2.04 1.92 3.9 2 Hist A2 1.43 0.54 11.2 0.77 2.12 1.6 3 Hist B 0.09 0.06 6.0 0.01 2.64 0.0 4 Hist C 0.12 0.06 5.0 0.01 2.78 0.0 1 A1 2.85 0.68 14.1 1.94 1.92 3.7 2 A2 1.54 0.66 11.2 1.02 2.12 2.2 3 B 0.05 0.06 5.5 0.00 2.71 0.0 4 C 0.12 0.06 5.0 0.01 2.78 0.0 2-year P1 = 0.82 inches (UDFCD, Fig. RA-1) I = 28.5(P1)/(10+Tc)^0.786 (Ref. 2, Eq RA-3) PIPE STANDARD FORM SF-3 STORM DRAINAGE SYSTEM DESIGN (RATIONAL METHOD PROCEDURE) CALCULATED BY: DIRECT RUNOFF TOTAL RUNOFF STREET TRAVEL TIME GDB JOB NO: DATE: Jan-16 PROJECT: Maverik CHECKED BY: DESIGN STORM: 100-year DESCRIPTION DESIGN POINT AREA DESIG. AREA (Acres) RUNOFF COEFF Tc (min) C A (Acres) I (in/hour) Q (cfs) Tc (min) (C A) (Acres) I (in/hour) Q (cfs) SLOPE (%) STREET FLOW (cfs) DESIGN FLOW (cfs) SLOPE (%) PIPE SIZE (in.) LENGTH (ft) VELOCITY (fps) Tt (min) REMARKS 1 Hist A1 2.92 0.82 14.1 2.39 6.69 16.0 2 Hist A2 1.43 0.72 11.2 1.03 7.40 7.6 3 Hist B 0.09 0.40 6.0 0.04 9.22 0.3 4 Hist C 0.12 0.40 5.0 0.05 9.70 0.5 1 A1 2.85 0.81 14.1 2.31 6.69 15.4 2 A2 1.54 0.79 11.2 1.22 7.40 9.0 3 B 0.05 0.40 5.5 0.02 9.46 0.2 4 C 0.12 0.40 5.0 0.05 9.70 0.5 100-year P1 = 2.86 inches (UDFCD, Fig. RA-6) I = 28.5(P1)/(10+Tc)^0.786 (Ref. 2, Eq RA-3) DIRECT RUNOFF TOTAL RUNOFF STREET PIPE TRAVEL TIME STANDARD FORM SF-3 STORM DRAINAGE SYSTEM DESIGN (RATIONAL METHOD PROCEDURE) CALCULATED BY: Project: Basin ID: Design Information (Input): Design Information (Input): Catchment Drainage Imperviousness Ia = 81.50 percent Catchment Drainage Imperviousness I a = 81.50 percent Catchment Drainage Area A = 4.390 acres Catchment Drainage Area A = 4.390 acres Predevelopment NRCS Soil Group Type = B A, B, C, or D Predevelopment NRCS Soil Group Type = B A, B, C, or D Return Period for Detention Control T = 2 years (2, 5, 10, 25, 50, or 100) Return Period for Detention Control T = 100 years (2, 5, 10, 25, 50, or 100) Time of Concentration of Watershed Tc = 14 minutes Time of Concentration of Watershed Tc = 14 minutes Allowable Unit Release Rate q = 1.25 cfs/acre Allowable Unit Release Rate q = 1.25 cfs/acre One-hour Precipitation P1 = 0.82 inches One-hour Precipitation P 1 = 2.86 inches Design Rainfall IDF Formula i = C1* P1 /(C2+Tc )^C3 Design Rainfall IDF Formula i = C1 * P1/(C2 +Tc)^C3 Coefficient One C1 = 28.50 Coefficient One C 1 = 28.50 Coefficient Two C2 = 10 Coefficient Two C 2 =10 Coefficient Three C3 = 0.789 Coefficient Three C 3 = 0.789 Determination of Average Outflow from the Basin (Calculated): Determination of Average Outflow from the Basin (Calculated): Runoff Coefficient C = 0.59 Runoff Coefficient C = 0.71 Inflow Peak Runoff Qp-in = 4.92 cfs Inflow Peak Runoff Qp-in = 20.63 cfs Allowable Peak Outflow Rate Qp-out = 5.49 cfs Allowable Peak Outflow Rate Qp-out = 5.49 cfs Mod. FAA Minor Storage Volume = 497 cubic feet Mod. FAA Major Storage Volume = 19,831 cubic feet Mod. FAA Minor Storage Volume = 0.011 acre-ft Mod. FAA Major Storage Volume = 0.455 acre-ft 5 <- Enter Rainfall Duration Incremental Increase Value Here (e.g. 5 for 5-Minutes) Rainfall Rainfall Inflow Adjustment Average Outflow Storage Rainfall Rainfall Inflow Adjustment Average Outflow Storage Duration Intensity Volume Factor Outflow Volume Volume Duration Intensity Volume Factor Outflow Volume Volume minutes inches / hr acre-feet "m" cfs acre-feet acre-feet minutes inches / hr acre-feet "m" cfs acre-feet acre-feet (input) (output) (output) (output) (output) (output) (output) (input) (output) (output) (output) (output) (output) (output) 5 2.76 0.049 1.00 5.49 0.038 0.011 5 9.62 0.207 1.00 5.49 0.038 0.169 10 2.20 0.078 1.00 5.49 0.076 0.003 10 7.67 0.329 1.00 5.49 0.076 0.254 15 1.84 0.099 0.97 5.32 0.110 -0.011 15 6.43 0.414 0.97 5.32 0.110 0.304 20 1.60 0.114 0.85 4.68 0.129 -0.015 20 5.57 0.478 0.85 4.68 0.129 0.349 25 1.41 0.126 0.78 4.29 0.148 -0.022 25 4.93 0.529 0.78 4.29 0.148 0.381 30 1.27 0.136 0.74 4.03 0.167 -0.030 30 4.44 0.572 0.74 4.03 0.167 0.405 35 1.16 0.145 0.70 3.85 0.186 -0.041 35 4.04 0.608 0.70 3.85 0.186 0.422 40 1.07 0.152 0.68 3.71 0.204 -0.052 40 3.72 0.639 0.68 3.71 0.204 0.435 45 0.99 0.159 0.66 3.60 0.223 -0.064 45 3.45 0.667 0.66 3.60 0.223 0.444 50 0.92 0.165 0.64 3.52 0.242 -0.077 50 3.22 0.692 0.64 3.52 0.242 0.450 55 0.87 0.170 0.63 3.45 0.261 -0.091 55 3.03 0.714 0.63 3.45 0.261 0.453 60 0.82 0.175 0.62 3.39 0.280 -0.105 60 2.85 0.735 0.62 3.39 0.280 0.455 65 0.77 0.180 0.61 3.34 0.299 -0.119 65 2.70 0.754 0.61 3.34 0.299 0.455 70 0.74 0.184 0.60 3.30 0.318 -0.134 70 2.57 0.772 0.60 3.30 0.318 0.454 75 0.70 0.188 0.59 3.26 0.337 -0.149 75 2.45 0.788 0.59 3.26 0.337 0.452 80 0.67 0.192 0.59 3.23 0.356 -0.164 80 2.34 0.804 0.59 3.23 0.356 0.448 85 0.64 0.195 0.58 3.20 0.375 -0.180 85 2.24 0.818 0.58 3.20 0.375 0.444 90 0.62 0.198 0.58 3.17 0.393 -0.195 90 2.15 0.832 0.58 3.17 0.393 0.439 95 0.59 0.201 0.57 3.15 0.412 -0.211 95 2.07 0.845 0.57 3.15 0.412 0.433 100 0.57 0.204 0.57 3.13 0.431 -0.227 100 2.00 0.858 0.57 3.13 0.431 0.426 105 0.55 0.207 0.57 3.11 0.450 -0.243 105 1.93 0.870 0.57 3.11 0.450 0.419 110 0.53 0.210 0.56 3.10 0.469 -0.259 110 1.87 0.881 0.56 3.10 0.469 0.412 115 0.52 0.212 0.56 3.08 0.488 -0.275 115 1.81 0.892 0.56 3.08 0.488 0.404 120 0.50 0.215 0.56 3.07 0.507 -0.292 120 1.75 0.902 0.56 3.07 0.507 0.395 125 0.49 0.217 0.56 3.05 0.526 -0.308 125 1.70 0.912 0.56 3.05 0.526 0.386 130 0.47 0.220 0.55 3.04 0.545 -0.325 130 1.65 0.922 0.55 3.04 0.545 0.377 Project Name: Maverik Job No. 15001770 Title: Existing Pond Date: Jan-16 Revised: By: GDB Tributary Area (ac.): 4.39 Drainage Basin: Basin A Volume Equation: Modified FAA V = Volume in cubic feet (cu-ft) h = Contour Interval in feet (ft.) A1,A2 = Area enclosed by successive Contours in square feet (sq-ft) Required Volume: Allowable Release Rate: WQCV = See Below Q100R = 5.5 cfs Minor Required Volume = 0.01 ac-ft 479 cubic feet 100 Year Required Volume = 0.46 ac-ft 19,820 cubic feet Contour Area A1+A2 (A1xA2)^1/2 (A1+A2) + h h/3 Volume Accumul. Accumul. Elev. (A1+A2)^1/2 Volume Volume (ft.) (sf) (sf) (sf) (sf) (ft) (ft) (cu-ft) (cu-ft) (ac-ft) 4927.5 5 5 0.00 600 55 655 0.50 0.17 109 4928 595 114 0.00 4448 1514 5962 0.50 0.17 994 4928.5 3853 1108 0.03 8750 4344 13094 0.50 0.17 2182 4929 4897 3290 0.08 10356 5170 15526 0.50 0.17 2588 4929.5 5459 5878 0.13 11474 5730 17204 0.50 0.17 2867 4930 6015 8745 0.20 12544 6267 18811 0.50 0.17 3135 4930.5 6529 11880 0.27 13601 6795 20396 0.50 0.17 3399 4931 7072 15280 0.35 4928.18 depth = 0.68 4931.67 depth = 4.17 100 Year Freeboard Elevation = 4932.67 Minor Water Surface Elevation (EURV) = 100 Year Water Surface Elevation (Incl WQCV) = 135 0.46 0.222 0.55 3.03 0.563 -0.342 135 1.61 0.931 0.55 3.03 0.563 0.368 140 0.45 0.224 0.55 3.02 0.582 -0.358 140 1.56 0.940 0.55 3.02 0.582 0.358 145 0.44 0.226 0.55 3.01 0.601 -0.375 145 1.52 0.949 0.55 3.01 0.601 0.348 150 0.43 0.228 0.55 3.00 0.620 -0.392 150 1.49 0.957 0.55 3.00 0.620 0.337 155 0.42 0.230 0.55 2.99 0.639 -0.409 155 1.45 0.965 0.55 2.99 0.639 0.326 160 0.41 0.232 0.54 2.99 0.658 -0.426 160 1.42 0.973 0.54 2.99 0.658 0.315 165 0.40 0.234 0.54 2.98 0.677 -0.443 165 1.39 0.981 0.54 2.98 0.677 0.304 170 0.39 0.236 0.54 2.97 0.696 -0.460 170 1.35 0.989 0.54 2.97 0.696 0.293 175 0.38 0.237 0.54 2.96 0.715 -0.477 175 1.33 0.996 0.54 2.96 0.715 0.281 180 0.37 0.239 0.54 2.96 0.734 -0.495 180 1.30 1.003 0.54 2.96 0.734 0.270 185 0.36 0.241 0.54 2.95 0.752 -0.512 185 1.27 1.010 0.54 2.95 0.752 0.258 190 0.36 0.242 0.54 2.95 0.771 -0.529 190 1.25 1.017 0.54 2.95 0.771 0.245 195 0.35 0.244 0.54 2.94 0.790 -0.546 195 1.22 1.023 0.54 2.94 0.790 0.233 200 0.34 0.245 0.54 2.94 0.809 -0.564 200 1.20 1.030 0.54 2.94 0.809 0.221 205 0.34 0.247 0.53 2.93 0.828 -0.581 205 1.18 1.036 0.53 2.93 0.828 0.208 210 0.33 0.248 0.53 2.93 0.847 -0.599 210 1.16 1.042 0.53 2.93 0.847 0.195 215 0.33 0.250 0.53 2.92 0.866 -0.616 215 1.14 1.048 0.53 2.92 0.866 0.183 220 0.32 0.251 0.53 2.92 0.885 -0.634 220 1.12 1.054 0.53 2.92 0.885 0.170 225 0.31 0.253 0.53 2.92 0.904 -0.651 225 1.10 1.060 0.53 2.92 0.904 0.157 230 0.31 0.254 0.53 2.91 0.923 -0.669 230 1.08 1.066 0.53 2.91 0.923 0.143 235 0.30 0.255 0.53 2.91 0.941 -0.686 235 1.06 1.072 0.53 2.91 0.941 0.130 240 0.30 0.257 0.53 2.90 0.960 -0.704 240 1.05 1.077 0.53 2.90 0.960 0.117 245 0.30 0.258 0.53 2.90 0.979 -0.721 245 1.03 1.082 0.53 2.90 0.979 0.103 250 0.29 0.259 0.53 2.90 0.998 -0.739 250 1.01 1.088 0.53 2.90 0.998 0.090 255 0.29 0.260 0.53 2.90 1.017 -0.757 255 1.00 1.093 0.53 2.90 1.017 0.076 260 0.28 0.262 0.53 2.89 1.036 -0.774 260 0.98 1.098 0.53 2.89 1.036 0.062 265 0.28 0.263 0.53 2.89 1.055 -0.792 265 0.97 1.103 0.53 2.89 1.055 0.048 270 0.27 0.264 0.53 2.89 1.074 -0.810 270 0.96 1.108 0.53 2.89 1.074 0.034 275 0.27 0.265 0.53 2.88 1.093 -0.827 275 0.94 1.113 0.53 2.88 1.093 0.020 280 0.27 0.266 0.53 2.88 1.111 -0.845 280 0.93 1.118 0.53 2.88 1.111 0.006 285 0.26 0.267 0.52 2.88 1.130 -0.863 285 0.92 1.122 0.52 2.88 1.130 -0.008 290 0.26 0.269 0.52 2.88 1.149 -0.881 290 0.91 1.127 0.52 2.88 1.149 -0.022 295 0.26 0.270 0.52 2.87 1.168 -0.899 295 0.89 1.132 0.52 2.87 1.168 -0.037 300 0.25 0.271 0.52 2.87 1.187 -0.916 300 0.88 1.136 0.52 2.87 1.187 -0.051 305 0.25 0.272 0.52 2.87 1.206 -0.934 305 0.87 1.141 0.52 2.87 1.206 -0.065 Mod. FAA Minor Storage Volume (cubic ft.) = 497 Mod. FAA Major Storage Volume (cubic ft.) = 19,831 Mod. FAA Minor Storage Volume (acre-ft.) = 0.0114 Mod. FAA Major Storage Volume (acre-ft.) = 0.4553 Determination of MAJOR Detention Volume Using Modified FAA Method (For catchments less than 160 acres only. For larger catchments, use hydrograph routing method) (NOTE: for catchments larger than 90 acres, CUHP hydrograph and routing are recommended) UDFCD DETENTION BASIN VOLUME ESTIMATING WORKBOOK Version 2.34, Released November 2013 Determination of MINOR Detention Volume Using Modified FAA Method DETENTION VOLUME BY THE MODIFIED FAA METHOD Maverik A 15001770-UD-Detention_v2.34, Modified FAA 1/15/2016, 11:15 AM Survey Area Data: Version 10, Sep 22, 2015 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Apr 22, 2011—Apr 28, 2011 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. Hydrologic Soil Group—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 11/16/2015 Page 2 of 4